Reciprocating motion can be converted into rotating motion through several different devices. As an example, reciprocating motion can be converted into rotating motion through a crank. In this type of device, the reciprocating motion is perpendicular to the axis of rotation. Alternatively, a “cam” type device can be used to convert reciprocating motion into rotating motion. In this later device, the cam wobbles on a rotating shaft and produces an axial reciprocating motion in the direction of the rotating axis. In this later device, the linear or reciprocating movement is parallel to the rotating axis.
In the description which follows, a swash or wobble plate engine is disclosed and can be characterized as an engine which utilizes a “cam” type mechanism.
Two-cycle engines are defined as engines with one power stroke per revolution rather than one power stroke every other revolution as in 4 cycle engines.
There are two types of opposed piston engines which include a swash plate. One engine type has a crank shaft or swash plate located between two opposed pistons. In this first engine type, each piston operates in a separate cylinder. The second engine type has two crank shafts or two swash plate mechanisms, with two opposed pistons sharing one cylinder located between the two crank shafts or two swash plate mechanisms. The internal combustion engine disclosed herein involves an opposed piston engine of the second type.
As used herein and throughout, the phrases “T.D.C.” and “B.D.C” refer to the extreme position of the piston in the cylinder at top and at bottom respectively. As used herein and throughout, the term or phrase “normal operating speed” refers to an average speed in the normal operating range. Thus, if the engine normally operates in a range from 1900 to 2600 rpm the normal operating speed would be 2250 rpm.
The swash plate mechanism of an internal combustion engine converts the reciprocating motion into a rotating motion by a cam. The cam in the form of a rotating disc fixed to a rotatable shaft at an angle to produce an inclined plane with respect to the centerline of the shaft. A non-rotating disc is in contact with the rotating surface on the angled rotatable shaft through a bearing. As the shaft rotates, the non-rotating disc wobbles. A mechanism is required to keep the non-rotating disc from rotating. A variety of mechanisms are known such as sliding bearings, linkages, universal joints, and bevel gears to allow motion between the discs and to keep the non-rotating disc from rotating.
Any point on the non-rotating disc moves back and forth essentially thru a circular arc in the direction of the axis of the shaft. Thus, a piston in linear motion parallel to the shaft, can operate against a point on the non-rotating disc thru a connecting rod assembly having ball joints at opposed ends.
The ball joints are necessary to accommodate the slight non-planar motion of the center of the ball joint on the non-rotating disc with respect to the center of the ball joint in the piston. The angular displacement of one ball joint with respect to the other varies from positive to negative depending on the angle of rotation of the engine
Internal combustion engines having one or more swash plates are known in the prior art. A serious problem with the prior art devices, however, involves how to deal with the relatively large forces generated during engine operation. The prior art has yet to develop an economical version of an internal combustion engine which utilizes swash plate technology and which is operational at relatively high speeds.
Swash plate mechanisms are used in compressors, hydraulic pumps and motors. These devices with swash plate mechanisms are widely used in industry, while engines with swash mechanisms are not. The reasons why swash plate technology are not used in internal combustion engines is both numerous and complex. First, the efficiency of sliding bearings used in pumps is low. This effect is accentuated in internal combustion engines. Second, if antifriction bearings are proposed, their load capacity is limited due to their proposed location within the engine and their installation is difficult. Larger bearings (unless they are located properly within the design) tend to increase the size of the engine and, thus, the acceleration forces which require still larger bearings. Thus, the speed of the engine in these proposals is limited due to the acceleration forces. Moreover, the mechanism for transmitting torque reactions from the non-rotating disc to the engine housing is difficult and space consuming. Proposals range from sliding mechanisms, to linkages, to U-joints, to small diameter bevel gears. Bevel gears are commonly used in swash plate compressors with relatively low pressure. They are small diameter gears located at the intersection of the axis of rotation of the main shaft and the axis of relative rotation of the bearing between the two swash plates. A high power density engine would need much larger diameter gears. These and other related problems make the swash plate engine uninteresting.
Most engines in the passenger car and truck industry are using a four cycle, crankshaft type system. Four-cycle engines, as opposed to two-cycle engines, however, require expensive valve systems including separate cylinder heads and in most cases separate intake and exhaust manifolds.
The following is a non-exhaustive list of reasons why two-cycle, crank type engines are not common. First, fuel needs and special lubricant additives which cause pollution during operation of a two-cycle engine is a drawback to two-cycle engine designs and are an inconvenience for the operator. Second, the gas exchange between the exhaust gas and the intake gas is inefficient in two-cycle engine designs whereby causing pollution and higher fuel consumption. This is due to the fact that the inlet port and the exhaust port are both located in relative proximity near the BDC of the piston. Thus, mixing of exhaust gas and intake gas is inevitable. Also, the timing of the various port openings and closings is compromised, as the exhaust port must open first to allow the pressure in the cylinder to drop to intake pressure before the intake port opens. Consequentially the intake port closes first before the exhaust port closes. This inherent timing prevents the filling of the cylinder to an intake pressure higher than the average exhaust pressure. Moreover, multi-cylinder two-cycle engines require a turbo charger or a compressor. An engine driven compressor causes significant losses and is generally ruled out for cars and trucks. Use of a turbo charger, however, is compromised since the timing problem mentioned above is accentuated. Some car and truck engines use a “pulse” type turbo charger which takes advantage of the kinetic energy in the exhaust, and keeps the average exhaust pressure lower than the intake pressure. But the inherent timing problem will not allow the fill pressure in the cylinder to exceed the exhaust pressure and, therefore, the turbo charger is not fully utilized. The present invention disclosure presents a two-cycle opposed piston design in combination with a swash plate mechanism which addresses and offers a unique solution to these heretofore known problems with two-cycle engines.
In general, crankshaft type, multi cylinder engines use journal bearings to carry the loads, since it is difficult to install antifriction bearings. One of the known problems with journal bearings, however, is that they have higher friction, thus, fuel consumption is increased. Also, in crank shaft type engines, the torque reaction of the output torque is transmitted to the housing through the piston pushing against the cylinder wall causing significant losses translating to higher fuel consumption.
Swash plate engine designs have been proposed before, but they have not found acceptance. Their acceptance in industry was largely hindered because of bearing problems and inefficiencies related to friction in sliding bearings. Also strength problems in the components within a compact design had a detrimental effect on their wide spread acceptance.
Use of antifriction bearings do not offer adequate capacity for high power density applications. Also, the torque reaction of the engine has heretofore been dealt with inadequately with proposals of sliding mechanisms, universal joints, linkages and small diameter bevel gears, which would not have sufficient capacity. Two-cycle opposed piston crank type engines, in which two pistons share the same cylinder, are also known in the art, but they were of the crank type and it would be cumbersome and space consuming to interconnect the two crank shafts.